I'm not sure I understand your question cause the answer is really straightforward, but here goes: Assuming your subs are properly timed, the easiest way to advance or delay when the subs start (i.e. synch with the video) is with Aegisub. With your subs loaded into Aegisub just go to the Timing tab and click Shift Times from the drop down list. Then simply adjust by however many seconds you want. You can do the whole vid or just a segment. You can do this multiple times if your subs are badly mistimed. Just save after each shift. If you don't know how much shift, simply load your vid and subs into MPC (FLV has a similar feature) and use the F1 and F2 keys to synch. Once it's in synch, note how many seconds you needed to move the subs to get synch. Then back into Aegisub to move the subs that same amount. Is this what you were asking?